Performance improvements
Removed functions that are the same as those in get_mda and separated the roi calculation so that memoization will discriminate based on roi limits (as it should)
getGoodPixels was removed from get_netcdf reader as it is the same as the get_mda reader
Performance improvements by refactoring, memoizing relevant bits and pre-computing file paths rather than doing them on-the-fly
Merge branch 'performance' into Sakura/master
Merge branch 'master' of https://github.com/Peter--K/Sakura into Sakura/master

Conflicts:
	get_mda.py
Caching lazy element reader that reads and caches complete contents of a file on attempting to read it for the first time.
Working caching netCDF reader without NormT correction
NormT normalization
Reset memoization for now.
Merged Peter's latest changes
Small change to tidy up indexing without resorting to numpy arrays
New UI for Sakura that maintains the ability to modify it using wxFormBuilder
Writes a colourmap as a 256x3-entry text file. By doing this, we can avoid matplotlib as a dependency when it comes time to bundle Sakura for distribution.
Temporary pre-range-selection checkin
Interim checking for ROI range selection
setup file for bundling with py2exe
Element detector UI tool behaviour change to allow locking of spectrum for range selection
Interim checkin - ROI overlay still misbehaving
Disallow selection of Spectrum panel for non-netCDF data